The present invention relates to a dual-polarized printed circuit antenna whose elements are capacitively coupled to feedlines. More specifically, the invention relates to a printed circuit antenna employing dual-polarization geometry having feedlines and radiating elements stacked one above the other with feedlines which are capacitively coupled to the radiating elements, such that no RF interconnection is required. By employing electromagnetic coupling in the power transfer from the distribution networks to the radiating elements, a high-performance, light weight, compact, low-cost dual polarized planar or conformal antenna is achieved.
Examples of previous work in the field of printed circuit antennas employing capacitive coupling made be found in currently co-pending U.S. Pat. Applications Ser. No. 748,637, filed June 25, 1985, now U.S. Pat. No. 4,761,654 and Ser. No. 930,187, filed November 13, 1986. These applications disclose printed circuit antennas employing capacitive coupling and enabling either linear or circular polarization, depending on the shape of the radiating and feeding elements (which may be patches or slots) which are used.
As shown in FIG. 1a, the ground plane 10, feedline 12, and feeding patch 14 are capacitively coupled. Alternative structures, employing radiating slots 16b, are shown in FIGS. 1b and 1c as well. The resulting structure is a light weight, low-cost, singly-polarized planar or conformal antenna capable of operating with either linear or circular polarization.
One limitation of this structure is that the antenna constructed according to the techniques disclosed in these co-pending applications can receive only one sense of polarization, either linear or circular, from a satellite. It is desirable to have a compact antenna structure which is capable of receiving both senses of polarization, so that twice as much information can be received.
One technique for achieving this desired result involves the provision of a dual-polarized antenna structure. However, because of problems inherent in the interaction among the various radiating elements and the power dividers in different layers in such a structure, it has not previously been possible to provide such an antenna.